its so weird, because I am a joe w, but I doubt that you meant me...
but in the case that you are, oddly enough. I've been looking long and hard at various wide angle lenses and decided that the 14-24 is brilliant, but really an FX beast, and its somewhat wasted on a DX camera... because what thats.. 21-36 roughly? Consider the sigma 10-20 is a 15-30... or the 12-24 even, is 18-36... theres alot of Angle missing on a crop camera with the 14-24... though hands down its optically the best, I believe.
For me it came down to
12-24 nikkor --- 12-24 tokina --- 10-20 sigma -- 11-16 tokina.
I dropped the nikkor off the list because of its price and size. The 12-24 tokina got knocked off for high CA, but is very close to the nikkor in many ways, cheaper, with more CA really. The others are also wider, and that meant alot. That lead me to the 10-20 siggy and the 11-16, This was where things really got tricky, as the lenses are both strong performers and have very different strengths and weaknesses.
In general, (sample variation or otherwise) The tokina is equivilent to or better than the sigma, in sharpness when stopped down. Various reviews rate the tokina exceptionally sharp. I heard alot of stuff otherwise, So I ignored this in my choice. The Sigma is a larger range, but in general that 1mm is easily adjusted for by a step back or forth... the longer end of the range is a much bigger difference, but with plenty of 18mm lenses at my disposal, it seemed just having UWA would be enough. The Tokina has more CA, but its lateral, and easier to adjust distortion, the sigma has weird moustache distortion at the widest end. The Tokina is faster, and that was relevant to me. Both have nice focus systems and in my case the price was the same. The Sigma appears to render color better while the tokina is more contrasty. (personal opinions) The sigma is smaller and lighter. They both feel nice, though the Tokina has a better build quality in my eyes. (I was able to hold the sigma at the store, I cant tell you how much heavier the tokina feels, it just does!)
In the end I went with the Tokina because they both cost the same, the Tokina was easily available, and I would rather have more versatility with the 2.8 for low light or random situations than the extra zoom range, I can usually move, but I cant usually make everything brighter. Eventually I may purchase the sigma as well... If I had been in the states, with an upcoming trip (like my soon trip into the Japanese alps) I wouldve gone with the cheaper sigma, but alas both being the same price, it just seemed worth it to go for the Tokina. (so far I am quite pleased with it, it seems to be a good copy, the Zoom range is a tad bit short, but already, I practically always have it at 11 anyway, id likely be using the sigma almost always at 10 as well.)
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A poor photographer blames his tools.
) and 24mm certainly isn't in the wide department.